Electrical Insulation Enamels Composed of Modified Polymers and Electrical Conductors Produced Therefrom and Having Improved Sliding Capacity

ABSTRACT

The present invention relates to electrical insulation enamels which contain a polymer comprising a base polymer and modifying units which are incompatible with the base polymer after the polymer has cured and lead to the formation of separate phases at the surface, and to processes for the production thereof. The electrical insulation enamels have a low coefficient of friction and frictional resistance and are preferably suitable for the coating of wires.

The present invention relates to electrical insulation enamels whichcontain a polymer comprising a base polymer and modifying units whichare incompatible with the base polymer after the polymer has cured andlead to the formation of separate phases at the surface, and toprocesses for production thereof. The electrical insulation enamels havea low coefficient of friction and frictional resistance are preferablysuitable for the coating of wires.

Electrical insulation enamels are used for coating wires which are usedas electrical conductors in electrical components such as coils, rotorsand stators. So as to produce these electrical components, the coatedwire is wound up using automated winding machines. In this context, theenamelled electrical wires should not be damaged on the edges of theelectrical components, and should be easy to insert into the grooves ofthe components, in such a way that a high packing density of the wire inthe electrical components can be achieved. High packing densities arenecessary so as to achieve optimum induction performance. A high packingdensity is also desirable because electrical machines, such as electricmotors, which contain electrical components of this type areincreasingly being miniaturised, since smaller and smaller devices andcomponents are increasingly sought after.

Therefore, so as to avoid incorrect laying of the wire in the electricalcomponents and to achieve high packing densities, the insulatedelectrical conductors should have a good sliding capacity. A goodsliding capacity further makes it possible to process the wire in modernhigh-speed winding robots, in which wire systems, braking systems andguide systems place extremely high stresses on the wire. A good slidingcapacity of the wire and the resulting sliding of the wires against oneanother improve the winding pattern on the coil. For these reasons, thefeature of sliding capacity of wires has developed into an importantquality feature for the production and processing of insulated wires.

Conventionally, so as to achieve a good sliding capacity of wires, anelectrical insulation enamel is initially applied which is based onself-crosslinking polyesters and polyester-imides, polyimides andpolyamide-imides and polyamides and polyesters which are crosslinkedwith blocked polyisocyanate adducts. Once the actual electricalinsulation layer has been applied to the wire, a lubricant is applied asan outer layer. Natural waxes, montan waxes, polyethylene waxes andcopolymers comprising propylene polymers of high α-olefins,polypropylene oxides, esters of high-functionality polyols andlong-chain fatty acids are used as lubricants. However, the use oflubricants of this type can be problematic, since in particularlubricants based on hydrocarbons, fatty acid esters and polypropyleneoxides are no longer stable at the very high application temperatures ofover 450° C. which are usual for electrical insulation enamels.Lubricants based on paraffin wax are usually in the form of a solutionin petroleum spirit. However, because of the evaporating petroleumspirit, lubricants of this type are problematic for environmentalreasons and for health protection reasons.

WO 2007/045575 discloses a lubricant for enamelled wires based on apolytetrafluoroethylene dispersion, which is intended to have improvedcoefficients of friction and is environmentally friendly. However, thelubricant has to be applied to the previously enamelled wire in aseparate process step.

A further approach to providing electrical insulation enamels having agood sliding capacity involves mixing a lubricant into the enamel. Anenamel of this type is disclosed for example in EP 0 823 120, in whichthe enamel contains polyethylene wax as an internal lubricant.

In a further approach to improving the sliding capacity of electricalinsulation enamels, the polymers contained in the enamel arefunctionalised with components. EP 0 033 224 and EP 0 072 178 discloseelectrical insulation enamels based on polymers, for examplepolyamide-imides, which are modified with terminal long-chain alkylgroups.

Electrical insulation enamels are further known in which polysiloxanesare physically mixed into the enamel or in which the polymers containedin the enamel are functionalised with polysiloxanes. For example, EP 1176 611 discloses insulated wires which comprise a polyamide-imide resinwhich is terminally modified with alkoxysiloxanes or aryloxysiloxaneswhich contain a glycide ether group. EP 0 447 789 discloses insulationenamels which contain a copolymer functionalised with polysiloxanes. Thepolysiloxanes used are not disclosed in greater detail. DE 20 00 638(U.S. Pat. No. 3,632,440) also discloses an insulation material in whichpolysiloxanes are mixed into a polymer resin or the polymer resin isfunctionalised by polysiloxanes. Functionalising the polymer resin withlong-chain polysiloxanes is not mentioned. US 2003/0215650 discloses themodification of polymer compounds with short-chain polysiloxanes.

An object of the invention is to provide an electrical insulation enamelwhich has a very good sliding capacity on the surface together with ahigh thermal resistance, flexibility and good dielectric properties.

This object is achieved in accordance with the invention by providing anelectrical insulation enamel which contains a functionalised polymercomprising a base polymer and modifying units which are incompatiblewith the base polymer after the polymer has cured, in particularthermally cured. The modifying units are in particular polysiloxanes.The modifying units are incompatible with the base polymer after curingor film formation, in such a way that self-structuring of the surfacetakes place. In this context, a phase separate from the base polymer isformed, and is present in particular at the outer surface of the curedenamel film and improves the sliding capacity properties of the enamelfilm.

The invention combines the advantageous properties of a base polymer,for example chemical stability and/or hardness, with the advantageousproperties of the modifying units, for example reduced adhesion and/orreduced friction. Since the modifying units are chemically fixed and inparticular covalently bonded to the base polymer, the modifying unitsare prevented from being deposited on the environment and in particularfrom bleeding out.

The electrical insulation enamel thus has in particular a phaseseparation on the surface, that is to say separate regions on thesurface formed from base polymer, and other separate regions formed frommodifying units. It has been found that the cured enamel according tothe invention has a structured anisotropic surface consisting of polarmatrix and non-polar separate regions. It has also been possible toestablish differences in the mechanical properties, namely in particulara rigid polar matrix, in particular a rigid polar base polymer matrixand particularly preferably a rigid polar polyamide-imide matrix, andsoft, “liquidy” separate regions, formed from modifying units, inparticular polysiloxanes, and even more preferably PDMS phaseseparations.

Electrical insulation enamels are usually in the form of colloidalsolution or a dispersion of polymer particles in a solvent. The polymerparticles may be in the form of colloidal particles or in the form ofgel particles. Gel particles may have modifying units on the outside,for example in a brush structure. Further components such as additivesmay be present if appropriate.

The polymers contained in the electrical insulation enamel according tothe invention comprise a base polymer which is functionalised ormodified with modifying units. The base polymers may for example beselected from the group consisting of polyamide-imides,polyester-imides, polyesters, polyamides, polyurethanes, polyimides,polyester-amide-imides, polyepoxides, and mixtures or combinationsthereof. In a preferred embodiment, the base polymer is apolyamide-imide and/or a polyester-imide, most preferably apolyamide-imide. The production of polymers of this type is known.

The base polymer may be selected depending on the intended use. For usein electrical insulation enamels, polyamide-imides and/orpolyester-imides are preferably used.

The polymers according to the present invention contain a base polymerwhich has at least one modifying unit. The modifying unit is inparticular a polysiloxane, preferably a polydialkylsiloxane and morepreferably a polydimethylsiloxane. The modifying units are in particularcoupled covalently to the base polymer.

As well as the polymer, the electrical insulation enamel also comprisessolvents, which are disclosed in the following. The solids content ofthe polymer in the electrical insulation enamel is usually at least 10%,at least 20%, at least 25%, at least 30%, at least 35% and up to 45%,50%, 60% or 70% (mass/mass). The electrical insulation enamel maycontain additives, which are disclosed in the following, as furthercomponents.

Surprisingly, it has been found that in the cured electrical insulationenamel, which can be obtained by curing, in particular thermal curing,separate regions occur on the surface. As a result, the coefficient offriction and the frictional resistance of the cured electricalinsulation enamels are improved. At the same time, good thermalresistance and flexibility are still obtained.

Modifying units according to the present invention are distinguished inthat when an enamel which contains a polymer comprising units of thistype is applied to a metal plate, for example an aluminium plate, or toa glass plate of a thickness of 5 μm to 20 μm, and after thermal curing,at a firing temperature of over 100° C., for example 150° C., 200° C.,220° C., 250° C. or 300° C., in particular of 250° C., and a firingduration of 2 to 15 minutes, preferably 10 minutes, separate regions arepresent on the surface. The proportion of these regions based on thetotal surface area may for example be determined by atomic forcemicroscopy.

The proportion of the separate regions on the surface in which modifyingunits are found—in particular when the content of blocks comprisingmodifying units is 20% by mass based on the polymer as a whole—ispreferably at least 5% by area, at least 15% by area, at least 20% byarea, at least 30% by area, at least 40% by area, at least 50% by areaand up to 60% by area, up to 70% by area, up to 80% by area, up to 90%by area or up to 95% by area, based on the surface as a whole.Accordingly, the proportion of regions on the surface in which basepolymer is found is at least 5% by area, at least 15% by area, at least20% by area, at least 30% by area, at least 40% by area, at least 50% byarea and up to 60% by area, up to 70% by area, up to 80% by area, up to90% by area or up to 95%, based on the surface as a whole.

The individual separate regions are preferably of a size of at least 0.1μm, preferably at least 0.2 μm. The size of the separate regions mayvary considerably, and may also be in the range of up to several μm, inparticular up to 10 μm, preferably up to 5 μm.

In one embodiment, the modifying units which are incompatible with thebase polymer after curing or film formation are long-chainpolysiloxanes. Polysiloxanes are chains of silicon atoms which arebonded to nitrogen atoms. The free valences of the silicon may beoccupied by side chains. In a preferred embodiment, the side chains aremutually independently alkyl, alkoxy, alkenyl, alkynyl, which areoptionally substituted with halogen, OH, COOH and/or amino. Preferredside chains are alkyl, preferably C₁-C₆ alkyl, in particular methyl.Accordingly, polydialkylsiloxanes (PDAS) and in particularpolydimethylsiloxanes (PDM) are particularly preferred as modifyingunits.

The end groups of the polysiloxanes may mutually independently befunctional groups selected from alkyl, alkoxy, alkoxy alkyl, alkynyl,aryl or heteroaryl, which may optionally be substituted with halogen,OH, COOH, cycloalkyl, epoxides and/or amino. The polysiloxanes arebonded to the base polymer via one or both end groups and/or one or moreside chains. The bonding takes place via at least one reactive group,which comprises for example OH—, SH—, COOH—, NH₂, CN—, OCN—, anhydride,epoxy and/or halogen groups and has reacted with a complementaryreactive group on the base polymer. There may be one or more reactivegroups, preferably one or two reactive groups on one or both ends of thesiloxane. Particularly preferably, there are two reactive groups on oneend of the polysiloxane.

The modifying units are preferably introduced into the base polymer viamodified blocks, for example monomers, which comprise the modifyingunits, bonded via reactive groups, which undergo a polymerisationreaction with unmodified blocks.

In a preferred embodiment, modifying units comprising a reactive groupcan be introduced into the polymer which is to be functionalised in thatthey are initially reacted for example with a trimeric monomer unit,such as a trimeric isocyanate adduct, in a molar ratio of 1:1. Theresulting compound may subsequently react with for example the remainingisocyanate group comprising the remaining reactive groups of the furthermonomers, and thus form a chain segment of a functionalised polymer.

Polysiloxanes consist of a plurality of siloxane units (Si units), whichare bonded to one another via nitrogen atoms. The polysiloxanes maycomprise 20 to 500 Si units, preferably 40 to 400 Si units, particularlypreferably 50 to 200 Si units, and most preferably 60 to 150 Si units.“Long-chain polysiloxanes” refers in particular to polysiloxanes whichcomprise at least 20, more preferably at least 30, even more preferablyat least 40 and in particular at least 60 Si units, and preferably up to500, particularly up to 300, in particular up to 200 and most preferablyup to 150 Si units.

In a preferred embodiment, the polysiloxanes are polydialkylsiloxanes,in particular polydimethylsiloxanes (PDMS). Suitablepolydimethylsiloxanes are for example

α-hydroalkoxy-ω-alkylpolydimethylsiloxanes (Formula I),

bis-(hydroxyalkoxyethyl)-polydimethylsiloxanes (Formula II),

α-carboxyalkoxypropyl-ω-butyl-polydimethylsiloxanes (Formula III), and

aminoproylpolydimethylsiloxanes (Formula IV). n is selected so as togive chain lengths in the range specified above. R represents an alkylfunctional group, in particular an alkyl functional group comprising 1to 30, in particular 2 to 6 carbon atoms.

Preferably, monofunctional or difunctional polydimethylsiloxanes areused. An α-difunctional polydimethylsiloxane is particularly preferred,for example as shown in Formula I. FIG. 2 shows somepolydimethylsiloxanes by way of example. In a particularly preferredembodiment, the polydimethylsiloxane isα-(2,2-dimethylolbutoxy)-propyl-ω-n-butylpolydimethylsiloxane. Theproduction of polydimethylsiloxanes of this type is known, as disclosedfor example in EP 0 430 216.

Even at relatively high contents by mass, because of the relatively highmolar mass thereof, polysiloxanes reduce the average molar mass of thepolymers, in particular of polyamide-imides and polyimides, by less thansmaller molecular blocks at comparable contents by mass. Therefore, thefilm properties of the electrical insulation enamels are virtuallyunaffected by the introduction of the modifying units.

In the polymer according to the invention, there are various embodimentsfor the arrangement of the modifying units, for example thepolysiloxanes, and the base polymer.

Modifying units may form chain-end-modified polymers (see for exampleFIG. 3 a) or a polymer chain of the modifying units with units of thebase polymer bonded thereto (see for example FIG. 3 b) with the basepolymer.

Difunctional or polyfunctional modifying units may form a linker-bondedpolymer (see for example FIG. 3 c) or a block copolymer (see for exampleFIG. 3 d) with units of the base polymer. In this context, the modifyingunit is preferably used which has two reactive groups on one of the endgroups and no reactive group on the other end group. This leads to themodifying group being inserted into the base polymer as a linker (seeFIG. 3 c). Alternatively, an α,ω-difunctional unit may be used, whichhas reactive groups on each end group. This leads to the formation of ablock copolymer (see also FIG. 3 d).

In a preferred embodiment, linker-bonded base polymer, in particularlinker-bonded polyamide-imide and/or polyester-imide, is used,polysiloxane, in particular polydimethylsiloxane, which preferably has60 to 80 Si units, for example approximately 65 Si units, acting as thelinker between the base polymer units, in particular polyamide-imidepolymer units and/or polyester-imide units (see FIG. 3 c).

In a further preferred embodiment, end-group-modified base polymer, inparticular end-group-modified polyamide-imide and/or polyester-imide, isused, the polysiloxane used, in particular polydimethylsiloxane,preferably comprising 60 to 80 Si units, for example approximately 65 Siunits (see FIG. 3 a).

In a further preferred embodiment, side-chain-functionalised modifyingunits, for example functionalised with aminoalkyl groups, are used, andreact with reactive groups, for example isocyanate groups, of the basepolymer, for example of a polyamide-imide and/or of a polyester-imide(see also FIG. 3 b).

In yet another embodiment, functionalised polymers are used in whichα,ω-bis-hydroxyalkyl-terminated polysiloxanes, in particularα,ω-bis-hydroxyalkyl-terminated polydimethylsiloxanes, form a blockcopolymer with the base polymer, for example a polyamide-imide and/or apolyester-imide (see FIG. 3 d).

Particularly advantageous results are achieved in relation to thesliding capacity of the electrical insulation enamel if combinations ormixtures of polymers are used comprising a plurality of differentmodifying units which are of different chain lengths, for example whichhave a different number of Si units. For example the combination ofpolymers is particularly preferred in which the first polymer isfunctionalised with a polysiloxane, in particular apolydimethylsiloxane, comprising approximately 60-80 Si units, and thesecond polymer is functionalised with a polysiloxane, in particular apolydimethylsiloxane, comprising approximately 120-140 Si units. Themass ratio of the first and second polymer is for example 10:90 to90:10, preferably 30:70 to 70:30, particularly preferably 40:60 to60:40, for example 50:50.

In a preferred embodiment, a chain-end-modified base polymer, inparticular a chain-end-modified polyamide-imide and/or polyester-imide(see FIG. 3 a), the end groups comprising 120-140 Si units, for exampleapproximately 132 Si units, is mixed in a mass ratio of 0.8:1.2 to1.2:0.8, and in particular of 1:1, with a linker-bonded base polymer, inparticular a polyamide-imide and/or polyester-imide (see FIG. 3 c), thepolysiloxane linker comprising 50 to 70 Si units, for exampleapproximately 65 Si units.

The content of the blocks comprising modifying units, based on thepolymer as a whole, is preferably 2 to 70% by mass, preferably 5 to 50%by mass, and particularly preferably 10 to 30% by mass. A content of theblocks comprising modifying units of 15-25% by mass is most stronglypreferred. Polymers comprising a higher content of modifying units maybe mixed with polymers comprising no modifying units. It is alsopossible to use mixtures of polymers comprising modifying units whichcontain different percentages by mass of modifying units with otherpolymers which do not contain any modifying units.

To produce the polymer comprising a base polymer and modifying units,polyols for example, which are used for the production of polyesters andpolyester-imides, can be reacted with carboxyl groups and anhydridegroups of the modifying units so as to form esters. Polycarboxylic acidsand polycarboxylic acid anhydrides, which are used for the production ofpolyesters, polyamides, polyester-imides, polyamide-imides andpolyimides, can be reacted with OH groups of the modifying units so asto form esters and with amino groups so as to form amides.Polyisocyanates, which are used for the production of polyester-imides,polyamide-imides and polyimides, can be reacted with OH groups of themodifying units so as to form urethane groups. Polyisocyanates can alsobe reacted with amino groups of the modifying units so as to form ureagroups.

For the production of self-crosslinking polyesters, terephthalic acid orterephthalic acid dimethyl ester and/or isophthalic acid, glycerol ortrishydroxyethyl isocyanurate and/or ethylene glycol are preferably usedas monomers. These monomers can also be used for the production ofpolyesters for crosslinking with blocked polyisocyanates.

Polyamides for electrical insulation enamels preferably consist ofaliphatic dicarboxylic acids and diamines and/or of lactams oraminocarboxylic acids.

Terephthalic acid or the dimethyl ester of terephthalic acid,trimellitic acid anhydride, glycerol or trishydroxyethyl isocyanurateand ethylene glycol are preferably used as monomers for the productionof polyester-imides.

Polyimides can be produced from tetracarboxylic acid dianhydrides,pyromellitic acid dianhydride (PMDA, 1,2,4,5-benzene tetracarboxylicacid dianhydride) preferably being used, and aromatic diioscyanates,4,4′ diisocyanatodiphenyl oxide and/or 4,4′ diisocyanatodiphenyl methane(MDI) preferably being used.

Polyamide-imides can be produced from tricarboxylic acid anhydrides,trimellitic acid dianhydride (TMA, 1,2,4-benzene tricarboxylic acidanhydride) preferably being used, and aromatic diisocyanates,4,4′-diisocyanatodiphenyl methane preferably being used.

A further subject-matter of the invention is a cured electricalinsulation enamel which can be obtained by curing, in particularthermally curing, an electrical insulation enamel according to theinvention, there being separate regions on the surface of the curedelectrical insulation enamel.

In this context, thermal curing comprises in particular thermaltreatment at 400° C. to 700° C., preferably at 450° C. to 600° C. andeven more preferably at 525° C. to 625° C.

A further aspect of the present invention is a process for theproduction of the electrical insulation enamel according to theinvention, characterised in that a first modified block, for example amonomer or a prepolymer, which comprises at least one modifying unit, ispolymerised with at least one second monomer, so as to obtain a polymercomprising modifying units, which is formulated together with a solventand optionally additives so as to form an electrical insulation enamel.

In a particularly preferred embodiment, the electrical insulation enamelaccording to the invention is produced in that a diisocyanate comprisinga polysiloxane is reacted with reactive groups, for example OH, COOH orNH₂, and the reaction product, for example a prepolymer, is subsequentlypolymerised with an acid anhydride.

The produced polymers, which are in the form of colloidal solutions ordispersions, are completed so as to form electrical insulation enamelswhich are capable of application. The polymers can be diluted to thedesired viscosity using suitable solvents. Preferably, the enamels whichare capable of application have a viscosity of 10 to 2500 mPa·s,preferably 100 to 800 mPa·s and particularly preferably 200 to 500mPa·s.

Suitable solvents for producing electrical insulation enamels are forexample cresols and xylenols, which optionally have a content of phenol,glycol ether, for example an oligoglycol ether such as methyl diglycol,glycol ether esters, such as butyl glycol acetate, propylene carbonate,higher alcohols, such as benzyl alcohol and diacetone alcohol, andhigher ketones, such as isophorone. To control the viscosity, forexample in relation to the solids for application, diluents may be used,for example aromatic hydrocarbons such as xylenes and C₃-C₅ aromatics,which may also contain alkyl naphthaline. Examples include Solvesso®100,Solvesso®150 and Solvesso®, commercial products from Exxon.

If polyisocyanates are used for the production of the functionalisedpolymers, polar solvents without reactive hydrogens are preferably used,such as N-methylpyrrolidone, N-ethyl pyrrolidone or N,N-dimethylacetamide. These process solvents constitute a component of theelectrical insulation enamel.

Further, additives such as catalysts and crosslinking partners areoptionally added. According to the present invention, the catalysts arefor example ester interchange catalysts, such as tetrabutyl titanate, orurethane exchange catalysts, such as organic tin salts. If polyestersare used as polymers, the amounts of blocked polyisocyanate necessaryfor the urethane crosslinking, for example isomer mixtures andderivatives of diisocyanatodiphenyl methane, blocked with cresols, maybe added as crosslinking partners. Further additives may for example bedefoaming agents and levelling agents.

A further aspect of the present invention relates to a process for theproduction of a coated wire, characterised in that a first modifiedblock, for example a monomer or a prepolymer, is polymerised with atleast one modifying unit comprising at least a second monomer, so as toobtain a polymer comprising modifying units, which is formulatedtogether with a solvent and optionally additives so as to form anelectrical insulation enamel, and the electrical insulation enamel isapplied to a wire and subjected to a firing process, there beingseparate regions on the surface of the cured electrical insulationenamel.

During the firing process, the film formation process of the electricalinsulation enamel takes place. In this context, the solvents evaporateand crosslinking reactions possibly take place. On the other hand, aphase separation of the polymer and the modifying units which areincompatible therewith takes place during the firing process. As aresult, the modifying units are orientated on the surface of theelectrical insulation enamel, resulting in an improved sliding capacitybeing achieved. The phase separation leads to an inhomogeneous surfaceof the electrical insulation enamel, which becomes apparent as a resultof a changed surface structure by comparison with electrical insulationenamel without modifying units. It is currently assumed that theincompatibility of the polymer with the modifying units results from thetendency of the polymer content to form polar interactions and from thetendency of the modifying units towards non-polar interactions.

The electrical insulation enamel according to the invention ispreferably used for application to a wire, in particular to a copperwire. Preferably, the wire constitutes an electrical conductor. Anelectrical conductor in accordance with the present invention is amedium which has freely movable charge carriers and is therefore capableof transporting electrical current. Preferred electrical conductorsaccording to the present invention are metals or metal alloys, inparticular copper and aluminium.

Wires are conventionally coated with different enamel materials in amulti-layer process. In a preferred embodiment, the electricalinsulation enamel according to the invention is therefore applied as anouter layer to a wire which is already coated with an electricalinsulation enamel without modifying units. The wire to which theelectrical insulation enamel according to the invention is applied as anouter layer can contain one or more electrical insulation enamelswithout modifying units as lower layers.

Preferably, the electrical insulation enamel which is produced accordingto the invention is applied to wires, preferably copper wires, usingconventional enameling machines, which may be in a horizontal andvertical arrangement. The wires may have diameters of 0.01 to 10 mm,preferably 0.01 to 3.0 mm, and may be flat wires or profile wires. Theelectrical insulation enamel is applied in 2 to 40 immersions,preferably 4 to 30, more preferably in 8 to 25 immersions, for exampleusing felt strippers or nozzle strippers. Subsequently, curing iscarried out. In this context, the electrical insulation enamel ispreferably fired in a circulating furnace having circulationtemperatures of 400° C. to 700° C., preferably 450° C. to 600° C., morepreferably 525° C. to 625° C. In a preferred embodiment, the enamelingprocess is continuous, and the enamelled wires travel at haul-off speedsof 20 to 250 m/min, preferably 60 to 200 m/min, more preferably 80 to140 m/min.

A further subject-matter of the invention is a wire, in particular acopper wire, which is coated with the electrical insulation enamelaccording to the invention. A further preferred subject-matter of theinvention is a wire, in particular a copper wire, which comprises anelectrical insulation enamel without modifying units and comprises anelectrical insulation enamel according to the invention as an outerlayer or layers.

The wires according to the invention comprising electrical insulationenamel may be used for various purposes, preferably for the productionof coils and windings on rotor armatures and stators for electric motorsand generators and for related electrical components.

A preferred embodiment of the invention is a coil which comprises awire, in particular a copper wire, which is coated with an electricalinsulation enamel according to the invention or which comprises anelectrical insulation enamel without modifying units and comprises anelectrical insulation enamel according to the invention as an outerlayer or layers.

Although the wire which is coated according to the invention already hasa very good sliding capacity, an external lubricant may additionally beapplied as an outer layer.

The invention further relates to the use of a polymer, comprising a basepolymer and modifying units which are incompatible with the base polymerafter the polymer has cured, as an electrical insulation enamel. Thebase polymer and the modifying units are in particular the materialsstated above, and preferably the materials emphasised above.

In a further embodiment of the invention, the polymers are present inthe electrical insulation enamel in the form of gel particles. These gelparticles contain modifying units, for example long-chain polysiloxanesand in particular long-chain polydimethylsiloxanes, on the surfacethereof. The modifying units may project outwards (polymer brushstructure). When a surface which contains a gel particle coating of thistype contacts a counter surface, for example a metal or non-metalsurface, such as a steel surface or a winding roll of a wire winder, thegel particles are stripped off from the enamel carrier, that is to saythe wire, and are thus available on both of the friction partners. Thisleads to a further reduction in the frictional resistance and thus to afurther improvement in the sliding capacity.

The invention further relates to the use of polydialkylsiloxane gelparticles in electrical insulation enamels and to electrical insulationenamels comprising polydialkylsiloxane gel particles. In this context,the long-chain polydialkylsiloxanes and in particularpolydimethylsiloxanes disclosed above are preferably used as thepolydialkylsiloxanes. It has been found that by way ofpolydialkylsiloxane (PDAS) gel particles of this type, and in particularby way of polydimethylsiloxane (PDMS) gel particles, a furtherimprovement in the sliding properties can be achieved. According to theinvention, gel particles of this type are introduced in particular intoan electrical insulation enamel. The PDAS gel particles and inparticular PDMS gel particles may in this context be introduced into aconventional insulation enamel, but also into a modified insulationenamel as disclosed herein.

The object of the invention is also achieved by way of an electricalinsulation enamel comprising a polymer and polysiloxane gel particles.In this embodiment, the advantageous properties of a base polymer, forexample chemical stability and/or hardness, are combined with theadvantageous properties of the modifying units, for example adhesionreduction and/or friction reduction, in that the release of themodifying units contained in the gel particles to the environment, andin particular bleeding out, is prevented or at least reduced by addingthe modifying units as gel particles.

The polysiloxanes which are contained in the polysiloxane gel particlesas modifying units are incompatible with the polymer after the polymerhas cured. They therefore form separate regions on the surface of thecured electrical insulation enamel after the polymer has cured. At thesame time, indirect escape of the modifying units is prevented, sincethe polysiloxane gel particles are bonded into the cured electricalinsulation enamel in a relatively stable manner.

The added polysiloxane gel particles are in particularpolydialkylsiloxane gel particles, the alkyl side chains preferablyhaving a length of 1 to 6 carbon atoms, and are particularly preferablypolydimethylsiloxane gel particles. The gel particles are in particularcrosslinked gel particles.

The base polymers disclosed above, and in particular polyamide-imides,polyester-imides, polyurethanes, polyesters, polyamides, polyimides,polyesteramide-imides, polyepoxides, and mixtures or combinationsthereof, may be used as polymers for the electrical insulation enamel.Polyamide-imides and polyester-imides are particularly preferred, andpolyamide-imides are most preferred. The polymers may be selecteddepending on the use of the enamel. In the case of use as anelectrically insulated wire, polyamide-imides and/or polyester-imidesare used in particular.

The invention further relates to a cured electrical insulation enamelwhich is obtained by thermally curing an enamel comprising a polymer andpolysiloxane gel particles. The thermal curing preferably takes place attemperatures of 400° C. to 700° C., preferably of 450° C. to 600° C.,and even more preferably at 525° C. to 626° C.

The present invention further relates to a process for producing anelectrical insulation enamel in which a polysiloxane gel particledispersion is mixed into an enamel containing a polymer. The enamelcontaining a polymer may be a conventional enamel or an enamel which ismodified as disclosed above.

The gel particles may in particular be mixed into polymeric coatings andbulk materials, in particular into enamels, as friction-reducingcomponents. In particular in enamels based on the polymers disclosedherein, and particularly preferably in electrical insulation enamels,for example based on polyamide-imide or polyester-imide, a majorreduction in the frictional resistance is found. These coatings furtherhave very low adhesion.

It has been found that by way of the siloxane gel particles according tothe invention a considerable reduction in the frictional resistance isachieved in coatings, in particular in polyamide-imide-based coatings.Polysiloxane gel particles have the advantage of an “additive solution”,that is to say they can be mixed into conventional coating systems orenamels in a simple manner.

It has further been found that gel particles may be transferred from thecoating onto the article during the friction process, and thus a furtherfriction reduction, for example by comparison with steel, is achieved.

By contrast, polysiloxane gel particles cannot migrate because of thecrosslinking thereof, and have better thermal stability thanpolydimethylsiloxane polyether block copolymers.

In a preferred embodiment, a polysiloxane gel particle dispersionaccording to the invention is produced by crosslinkingvinyl-group-functionalised polysiloxanes withhydride-group-functionalised polysiloxanes in a dispersing agent.Dispersions can be worked into an electrical insulation enamel so as toprovide an enamel having lower friction. However, there is also theoption of working in the gel particle dispersion beforehand, during theproduction of an enamel. The crosslinked gel particles are orientated onthe surface of the enamel layer, and lead to a sustained improvement inthe sliding capability of the surface which is coated with an enamel ofthis type.

Polysiloxane gel particle dispersions and production processes fordispersions of this type are further disclosed herein.

According to the invention, in a particularly preferred embodiment theseare polydialkylsiloxane gel particles, the alkyl side chains preferablybeing of a length of 1 to 6 carbon atoms, and these are most preferablypolydimethylsiloxane gel particles.

The gel particles are preferably produced as a dispersion of the gelparticles in a dispersing agent. The gel particles are preferablysynthesised to form a gel particle dispersion in polar media.Preferably, the prepolymers or monomers of the gel particles areinsoluble or only poorly soluble in the dispersion media. NMP((N-methyl-2-pyrrolidone), NEP (N-ethylpyrrolidone), DMAP(dimethylpyrrolidone), DMAc (dimethylacetamide), DMF(dimethylformamide), water or aqueous solutions and/or DMSO (dimethylsulfoxide) are preferably used as matrix or dispersion agents for thedispersion. A dispersion in N-methyl-2-pyrrolidone is particularlypreferred.

A dispersion of this type of polysiloxane gel particles, in particularof PDAS and more preferably of PDMS gel particles, can be mixed intocoating systems as a component, and thus act as a friction-reducingcomponent. The emulsion can be stabilised by functional monomersthemselves and/or by an emulsifying agent.

The gel particles according to the invention can be produced in variousmanners. The production of a dispersion from crosslinked polysiloxanegel particles is preferred, in particular from crosslinkedpolydialkylsiloxane gel particles, and most preferably from crosslinkedpolydialkylsiloxane gel particles, by means of in situ synthesis.However, the gel particles may also be produced by addition curing(hydrosilylation) or by emulsion polymerisation. In this context, theproduction may take place in an aqueous or non-aqueous matrix.

Vinyl-functional siloxane prepolymers in combination withhydride-functional siloxane prepolymers are preferably used as thestarting material. The reactive groups react with one another byhydrosilylation, and form crosslinked polysiloxane gel particles. Thecrosslinking may be assisted by way of a suitable catalyst. There isalso the option of only using vinyl-functional polysiloxanes andcarrying out radical crosslinking, for example by means of a peroxideinitiator.

Dispersions comprising PDMS gel particles in NMP(N-methyl-2-pyrrolidone) are particularly preferred.

In a preferred embodiment, the gel particles according to the inventionconsist exclusively of polysiloxanes, in particularpolydimethylsiloxanes, which are bonded to one another via reactivegroups, such as vinyl groups or hydride groups. However, it is alsopossible to provide gel particles which contain a core, in particular anSiO₂ core or a polymer core.

The gel particles according to the invention may be used in addition topolymers containing modifying units, for example so as to achieve areduction in friction. However, there is also the option of usingpolysiloxane gels instead of modified polymers, that is to say inconventional enamels or coating materials.

In the following, some particularly preferred starting materials forpolysiloxane gel particles are described:

Vinyl-terminated polydimethylsiloxanes

wherein n is a whole number from 0 to 2000. Preferably, n is at least10, more preferably at least 20, even more preferably at least 30 and upto 1000, more preferably up to 500.

Vinylmethylsiloxane dimethylsiloxane copolymers,trimethylsiloxy-terminated

In the formula, the dimethylsiloxane and vinylmethylsiloxane groups mayoccur in any desired sequence. In this context, n denotes thevinylmethylsiloxane content in mol % and is between 0.5 and 1.5,preferably between 0.8 and 1.2. m represents the content ofdimethylsiloxane in mol %, and is calculated as m=100−n.

Vinylmethylsiloxane dimethylsiloxane copolymers,trimethylsiloxy-terminated, are characterised by the viscositiesthereof. According to the invention, viscosities of 250 cSt to 500,000cSt may be used, in particular viscosities of 1000 cSt to 100,000 cSt.

Vinyl-Functional Macromers

Macromers of this type serve as “dangling ends” and/or for producingpolymer brush surfaces. Suitable vinyl-functional macromers are forexample asymmetric monovinyl-terminated polydimethylsiloxanes, inparticular compounds of the formula

wherein n may be a whole number from 0 to 2000. n is preferably at least10, more preferably at least 20 and even more preferably at least 30 andup to 1000, more preferably up to 500.

The following structures, for example, may preferably be used ashydride-functional siloxane prepolymers:

Trimethlsiloxy-terminated methylhydrosiloxane dimethylsiloxanecopolymers, in particular of general formula

The methylhydrosiloxane and dimethylsiloxane groupings may be in anydesired arrangement in the copolymers. In each case, m represents thecontent of methylhydrosiloxane and n represents the content ofdimethylsiloxane units. Terminated trimethylsiloxy-methylhydrosiloxanedimethylsiloxane copolymers having a molar mass of 900 g/mol up to amolar mass of 50,000 g/mol may be used for the production of the gelparticles according to the invention.

Hydride-Terminated Methylhydrosiloxane Dimethylsiloxane Copolymers, inParticular of the Formula

In this context, the dimethylhydrosiloxane and dimethylsiloxane unitsmay be in any desired arrangement. m represents the content ofmethylhydrosiloxane units and n represents the content ofdimethylsiloxane. m, that is to say the content of methylhydrosiloxanein mol %, is preferably 5 to 20, more preferably 7 to 8. n, that is tosay the content of dimethylsiloxane in mol %, is preferably 90 to 95,more preferably 92 to 93. Preferably, m, that is to say the content ofmethylhydrosiloxane units in mol %, is preferably 10 to 90, morepreferably 20 to 40, and even more preferably 25 to 30. n, that is tosay the content of dimethylsiloxane in mol %, is preferably 50 to 90,more preferably 60 to 80 and most preferably 70 to 75. The molecularweight of the hydride-terminated methylhydrosiloxane dimethylsiloxanecopolymers used is preferably 2000 to 2600 g/mol.

Hydride-terminated polydimethylsiloxanes, in particular of the formula

wherein n is a whole number from 3 to 300, in particular from 4 to 230.

Crosslinked siloxane gel particles, in particular dispersions ofcrosslinked PDMS gel particles, may advantageously be worked into enamelor coating systems. Preferably, the PDMS gel particle dispersions whichare preferred herein are worked into NMP in conventional NMP-basedpolyamide-imide enamels, in particular electrical insulation enamels.They may be worked in for example using a Dispermat or an Ultra-Turrax.It is also possible to work the gel particles into modified enamels, inparticular into modified polyamide-imide electrical insulation enamels.The gels, in particular in the form of a gel particle dispersion, mayalso be worked into other enamels and in particular into otherelectrical insulation enamels, for example into polyester-imideelectrical insulation enamels, polyester electrical insulation enamels,polyimide electrical insulation enamels, polyamide electrical insulationenamels/thermosetting enamels and/or polyurethane electrical insulationenamels/thermosetting enamels.

In a further preferred embodiment, the gel particles are gel particlescomprising a hard silica core, in particular PDMS brush particlescomprising a hard silica core. In this context, silicate particles areused as starting particles. Particles of this type preferably consist ofpyrogenic silicic acid. Preferably, silicon dioxide particles are used,of which the surfaces comprise hydroxyl and/or vinyl groups. Siloxanesare subsequently suspended on the hydroxyl and/or vinyl groups of thesilicon dioxide particles. This may take place by adding ahydride-functional siloxane, optionally in the presence of a catalyst,for example a platinum catalyst. The bonding takes place by way of ahydrolysis reaction. The hydride-functional siloxane which is used maycomprise one or more Si—H functions. The molar mass may also be varied,and is preferably between 200 and 100,000, more preferably between 500and 5000 g/mol.

Alternatively, a hydride-functionalised siloxane may be reacted with avinyl-functional silazane. Subsequently, the vinyl-terminated orsilazane-terminated siloxane can react with hydroxyl groups of silicateparticles. Alternatively, chlorodialkyl vinyl silanes, in particularchlorodimethyl vinyl silanes, may also be used.

In the following, the invention is explained by way of preferredembodiments and drawings, although these do not limit the scope ofprotection of the invention.

DRAWINGS

The phase separation of the polymers and the modifying units is clearfrom FIGS. 1 a and 1 b.

FIG. 1 a is an atomic force microscopy photograph of the surface of theelectrical insulation enamel according to the invention based on apolyamide-imide polydimethylsiloxane block copolymer, thepolydimethylsiloxanes comprising approximately 63 Si units. Theelectrical insulation enamel is applied to a metal plate.

A major phase separation can be seen on the surface of the electricalinsulation enamel between the modifying units, which can be seen as darkbubbles, and the polymer.

FIG. 1 b shows an atomic force microscopy photograph of the surface ofan electrical insulation enamel based on a polyamide-imidepolydimethylsiloxane block copolymer, the polydimethylsiloxanescomprising approximately 10 Si units. The electrical insulation enamelis applied to a metal plate.

No major phase separation can be seen between the modifying units andthe polymer.

The comparison between FIG. 1 a, where a polydimethylsiloxane having achain length of 63 Si units is used, and FIG. 1 b, where apolydimethylsiloxane having a much shorter chain length of 10 Si unitsis used, clearly shows that a phase separation only occurs for a polymerhaving modifying units according to the present invention.

FIG. 2 a-g show suitable polydimethylsiloxanes for the electricalinsulation enamel according to the invention.

FIG. 3 a-d show various embodiments of the polymers according to theinvention.

FIG. 4 shows a D3 atomic force microscopy photograph of the surface of acoating of a polyamide-imide which is functionally modified with apolydimethylsiloxane. The brightly displayed regions are mobile butfixed siloxane segments.

EXAMPLES Example 1 Production of a polyamide having a 20% content ofα-(2,2-dimethylolbutoxy)-propyl-ω-n-butylpolydimethylsiloxane-functionalisedpolymer

300.0 g N-methylpyrrolidone (NMP) and 250.0 g xylene—as a processsolvent—and 293.5 g 4,4′-diioscyanatodiphenylmethane (MDI) are weighedinto a glass laboratory reactor of 2 l total volume, equipped with anelectrical resistance heater having temperature monitoring and control,comprising an agitator and a reflux cooler and the introduction ofprotective gas (nitrogen), and the reaction mixture is gently heated.The MDI is dissolved in the previously introduced solvent at 45° C.Subsequently, 104.0 g of theα-(2,2-dimethylolbutoxy)-propyl-ω-n-butylpolydimethylsiloxane, whichcomprises approximately 63 Si units, are metered in over a period of 15minutes, whilst the temperature is kept at 45° C. Subsequently, thereaction mixture is heated to 70° C., and is stirred for one hour at 70°C. Subsequently, the reaction mixture is cooled to 45° C., and 218.0 gtrimellitic acid anhydride (TMA) are added. Subsequently, the mixture isstirred for one hour at 45 to 50° C. Subsequently, the temperature isincreased in steps while stirring: 30 minutes at 65° C., then 30 minutesat 75° C., then 60 minutes at 85° C., then 60 minutes at 100° C., andfinally 60 minutes at 130 to 140° C. In the process, the reactionproduct carboxylic acid dissociates from the carboxyl groups andisocyanate. The reaction mixture reaches a viscosity (measured on asample in the cone/plate viscometer at 30° C.) of 6 Pa·s. It is cooledto less than 60° C., and 6.1 g ethanol are added so as to halt thereaction. The resulting colloidal solution has a solids content of 48%(measured at 1 hour at 130° C. in the circulating furnace). The contentof incompatible polydimethylsiloxane is 20% by mass, based on thepolymer as a whole (solids).

Control Example (VB) Production of a Polyamide-Imide without ModifyingUnits

The procedure is the same as in Example 1, but without the addition ofthe incompatible polydimethylsiloxane. 300.0 g NMP and 250.0 g xylene asa process solvent are weighed into the laboratory reactor describedabove, and 293.5 g 4,4′-diioscyanatodiphenylmethane are dissolvedtherein at 45° C. Subsequently, 223.1 g TMA are added. Subsequently, themixture is stirred for one hour at 45 to 50° C. Subsequently, thetemperature is increased in steps while stirring: 30 minutes at 45° C.,then 30 minutes at 75° C., then 60 minutes at 85° C., then 60 minutes at100° C., and finally 60 minutes at 130 to 140° C. In the process, thereaction product carboxylic acid dissociates from the carboxyl groupsand isocyanate. The reaction mixture reaches a viscosity (measured on asample in the cone/plate viscometer at 30° C.) of 6 Pa·s. It is cooledto less than 60° C. The resulting colloidal solution has a solidscontent of 42.9% (measured at 1 hour at 130° C. in the circulatingfurnace).

Example 2 Production of a polyamide-imide having a 20% content ofα-(2,2-dimethylolbutoxy)-propyl-ω-n-butylpolydimethylsiloxane-functionalisedpolymer

The procedure is the same as was described in Example 1. The amounts tobe weighed in are given in Table 1.

Example 3 Production of a polyamide-imide having a 5% content ofω-(2,2-dimethylolbutoxy)-propyl-ω-n-butylpolydimethylsiloxane-functionalisedpolymer

The procedure is the same as was described in Example 1. The amounts tobe weighed in are given in Table 1.

Example 4 Production of a polyamide-imide having a 20% content ofaminopropyl-polydimethylsiloxane-functionalised polymer

547.6 g NMP and 228.0 g TMA are weighed into the apparatus described inExample 1. The TMA is dissolved while stirring at 70° C. Subsequently,102.5 g of an aminopropyl polydimethylsiloxane, which comprisesapproximately 65 Si units, are metered in over a period of 15 minutes.The mixture is heated to 120° C., and subsequently kept at 120° C. for 1hour so that the polydimethylsiloxane can be reacted to exhaustion. Itis subsequently cooled to 40° C. and subsequently 280.0 g MDI are addedover a period of one hour. It is heated to 85° C. over a period of 2hours and subsequently to 130° C., until a viscosity of 6 Pa·s isreached (measured in the plate/cone viscometer at 30° C.). Subsequently,the reaction mixture is cooled. The resulting product has a solidscontent of 46.9% (measured at 1 hour at 130° C. in the circulatingfurnace).

Example 5 Production of a polyamide-imide having a 20% content ofhydroxyethoxypropyl-polydimethylsiloxane-functionalised polymer (thepolydimethylsiloxane comprises approximately 132 Si units)

The procedure is the same as was described in Example 1. The amounts tobe weighed in are given in Table 1.

TABLE 1 Examples of polyamide-imides comprising modifying units andcontrol example Components [g] B1 B2 B3 B4 B5 VB N-methyl- 300.0 300.0300.0 547.6 300.0 300.0 pyrrolidone Xylene 250.0 250.0 250.0 — 250.0250.0 4,4′-diioscyan- 293.5 293.5 293.5 270.0 293.5 146.8 atodiphenylmethane (MDI) Trimellitic acid 218.0 218.0 218.0 228.0 224.0 111.6anhydride (TMA) α-(2,2-dimethyl- 104.0 46.0 22.0 — — — olbutoxy)-propyl-ω-n-butylpoly- dimethylsiloxane Aminopropyl — — — 102.1 — —polydimethyl- siloxane 2-hydroxyethoxy- — — — 105.0 — propyl polydi-methylsiloxane NMP — — — 33.1 — — Ethanol 6.1 6.1 6.1 6.1 6.1 —Separated CO₂ 101.4 102.4 102.85 93.7 102.8 103.2 Total 1070.2 1011.2986.7 1093.6 1075.2 963.4 Solids [%] 48.6 45.6 44.3 46.9 48.3  42.9 (1h, 130° C.) Content of 20 10 5 20 20 — polymer comprising modifyingunits [%]

Examples 6-11 Electrical Insulation Enamels

Electrical insulation enamels were produced from the polymer solutionsdescribed in Examples 1-5 and the control example, by adding solvents.The composition of the electrical insulation enamels is shown in Table2.

TABLE 2 Electrical insulation enamels Number of Si units in the poly-dimethyl- Component siloxane [g] chain B6 B7 B8 B9 B10 B11 Polymer Ex. 1approx. 488.8 — — — 244.4 — (20% 63 modification) Polymer Ex. 2 approx.— 502.8 — — — — (10% 63 modification) Polymer Ex. 3 approx. — — 488.8 —— — (5% 63 modification) Polymer Ex. 4 approx. — — — 502.8 — — (20% 65modification) Polymer Ex. 5 approx. — — — — 244.4 — (20% 132 modification) Polymer — — — — — — 502.8 control example N-methyl- 156.2119.8 98.5 617.5 118.4 82.9 pyrrolidone N,N- 32.3 31.2 29.4 56.1 30.429.3 dimethyl- acetamide Total 677.4 653.8 616.7 1176.4 637.6 615.0Solids [%] (60 35.1 35.1 35.1 20.0 35.1 35.1 min., 130° C.) Viscosity710 860 780 350 660 830 [mPa · s] (plate/cone viscosity)

Applications of the Electrical Insulation Enamels

The electrical insulation enamels shown in Table 2 were enamelled on ahorizontally operating wire enameling machine at an ambient temperatureof at most 605° C. The blank wire diameter was 0.53 mm, and the haul-offspeed was 122 m/min. The application was carried out by way ofimmersions using nozzle strippers. There was a total of 10 passes. Theapplication for the first 7 passes consisted of a conventionalcommercial polyester-imide electrical insulation enamel, using a nozzlesequence of 560/570/570/580/580/590/590 μm. The following 2 applicationsconsisted of a conventional commercial polyamide-imide electricalinsulation enamel, using a nozzle sequence of 590/600 μm. The finalapplication consisted of the insulation enamel according to theinvention in accordance with Examples 6-10 or the enamel from thecontrol example in accordance with Example 11, using a nozzle having a610 μm opening diameter.

Testing the Sliding Capacity

As well as testing the thermal resistance and electrical properties, thesliding capacity was determined by two methods.

1. Measuring the Surface Resistance in Accordance with ParuselCoefficient of Friction

When the surface resistance is measured in accordance with the Paruselcoefficient of friction, an enamelled wire is passed between a polishedsteel surface and a steel slide lying thereon. The force which acts onthe steel slide is measured. This results in a (dimensionless)coefficient of friction. Low values of the coefficient of friction meanlow friction (tensiometry, see DIN EN 60851).

2. Measuring the Frictional Resistance in Accordance with Scintilla

An enamelled wire is passed at high speed under a steel block having aparticular contact surface area. The force which is produced by thefriction is measured. The result is in newtons (N).

Table 3 shows the measurement results for the enamelled wires and forthe enamelled wire using the control example.

TABLE 3 Measurement results for frictional resistance Measurementmethod/ example B6 B7 B8 B9 B10 B11 Number of Si units appr. 63 appr. 63appr. 63 appr. 65 appr. 132 — Parusel CoF (DIN EN 60851) 0.120 0.1300.210 0.132 0.099 0.230 Scintilla [N] 5.50 6.50 7.00 5.50 5.50 14.00

The measurement results shown in Table 3 demonstrate the advantage ofthe electrical insulation enamel according to the invention (B6-10) overan electrical insulation enamel without modifying units (B11). Thehigher the content of the modifying units in the polymer (cf. B6 20%, B710%, B8 5%), the lower the coefficient of friction and the frictionalresistance are. A particularly low coefficient of friction is achievedby mixing two polymers, comprising modifying units which comprise adifferent number of Si units, in a mass ratio of 50:50 (see B 10).

Example 12 Production of a Polyester-Imide Modified withPolydimethylsiloxane (PDMS)

A laboratory reactor (V4A, glass) having indirect heating (for exampleheat transfer oil) or controllable electrical resistance heating,product temperature monitoring, protective gas introduction, acontinuously controllable maximally edge-to-edge agitator, a fillingbody column with head temperature measurement, bridge and descendingreflux cooler (all distillate collected) is used as the reaction vessel.The column is moved as a dephlegmator.

The total amount of polyols (THEIC or glycerol, ethylene glycol),dimethyl terephthalate and 0.3% (based on the yield amount of thepolyester-imide as a whole=nfA) butyltitanate are weighed in the statedsequence (see also recipe in Table 4). Subsequently, entrainer is added:Solvesso 150 as approximately 3% of total amount weighed in.

Starting to introduce the protective gas (most preferably nitrogen, butcarbon dioxide or a mixture thereof with N₂ can also be used).

The reaction mixture is rapidly heated to approximately 160° C.Subsequently, the temperature is increased to max. 240° C. continuouslyover 5 hours. The time measurement is determined by the distillationprocess; the column head temperature should not exceed 75° C. (somewhatabove the boiling point of methanol, 64.7° C.). The methanol which hasdistilled off is collected and the amount thereof is determined (densityat 20° C.=0.7869). The reaction mixture is kept at 240° C., until nomore methanol accumulates. Subsequently, the mixture is cooled to lessthan 140° C.

Subsequently, amine-functional polydimethylsiloxane is added.Trimellitic acid anhydride and 4,4′-diaminophenyl methane is added as asolid mixture, but at least in alternating portions. Subsequently, themixture is heated again cautiously. The diimide carboxylic acid formsspontaneously and precipitates out. Enough Solvesso 150 is added to makethe dispersion easy to stir.

Subsequently, the mixture is initially heated slowly to up to 240° C.The time measurement is determined by the distillation process; thecolumn should not flood and the column head temperature should notexceed 105° C. (somewhat above the boiling point of water).

From 200° C. upwards, samples for measuring the acid number andviscosity are obtained. The acid number is determined by titration using0.5 molar alcoholic KOH against phenolphthalein on a sample dissolved inpreneutralised solvent [DIN 53169]. The dynamic viscosity is determinedusing a sample nfA 60% in solvent.

The reaction mixture is kept at 220° C. until the acid number is below20 mg KOH/g.

Subsequently, the laboratory reactor is switched to the short path(descending distillation bridge, best for determining the distillationtemperature) and the entrainer and residual water are distilled off. Themixture is kept at 220° C. until the intended characteristic values arereached.

Subsequently, the mixture is cooled to well below 170° C., and partiallydissolved, by adding approximately 5-10% of the intended amount ofsolvent, before cooling again. At less than 130° C., the content of thelaboratory reactor is discharged and further dissolved in the mainamount of the solvent.

Final characteristic nfA (60 min., 130° C.): 70.0 ± 1.0% values to beset: Acid No. (solid): 5-15 mg KOH/g Viscosity (dyn.): ±50 mPa · s(original partial dissolution, 23° C.)

TABLE 4 Recipe: Components [g] Weigh in [g] Dimethylterephthalate 64.02Trimellitic acid anhydride 84.48 N,N′-diaminodiphenylmethane 43.56Trishydroxyethyl isocyanate 96.18 Glycerol 0.00 Ethylene glycol 21.48Modifier: amine-functional PDMS, for example: Aldrich: 30.86 480304Poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane] Catalysts andsolvents: Butyltitanate 0.99 Solvanol PCA (or cresols/phenols) or xylene9.90 Solvesso 150 9.90 Total, weighed in polymer blocks 340.58 Totalmethanol release 7.69 Total H₂O release 2.33 Modification content [%]10%

Example 13 Production of a polyamide-imide comprising a 5% content ofaminopropylmethylsiloxane dimethylsiloxane copolymer modifier PDMSModifier

Molecular Mole % Code weight (aminopropyl) (ABCR) Viscosity [g/mol]MeSiO AMS-132 80-100 4500-5500 2.0-3.0 AMS-152 120-180  7000-80004.0-5.0 AMS-162 80-120 4000-5000 6.0-7.0 AMS-132: (2-3%aminopropylmethylsiloxane) dimethylsiloxane copolymer AMS-152: (4-5%aminopropylmethylsiloxane) dimethylsiloxane copolymer AMS-162: (6-7%aminopropylmethylsiloxane) dimethylsiloxane copolymer

100 g NMP, 50 g xylene and 45.6 g trimellitic acid anhydride (TMA) areweighed into a glass laboratory reactor having 0.5 l total volume,equipped with electrical resistance heating with temperature monitoringand control, with an agitator and a reflux cooler and the introductionof nitrogen. The TMA is dissolved at 70° C. while stirring.Subsequently, 4.6 g of the PDMS modifier, which comprises approximately70-100 Si units, are metered in over a period of 15 min. The mixture isheated to 120° C., and subsequently kept at 120° C. for one hour so asto react the PDMS component to exhaustion. It is subsequently cooled to40° C., and subsequently 58.7 g MDI are added over a period of one hour.The mixture is heated to 85° C. over a period of two hours, andsubsequently to 130° C. until a viscosity of 5 Pa·s (measured in theplate/cone viscometer at 30° C.) is achieved. Subsequently, the mixtureis cooled to 70° C., and by adding 1.2 g ethanol, the remaining freeisocyanate functions are reacted. The resulting product has a solidscontent of 47-51% (measured at 1 hour, 130° C. in the circulatingfurnace): AMS-123: 51% solids; AMS-152: 47% solids; AMS-162: 48% solids.

Application and Firing Conditions

The PAI which had been functionalised with AMS-132 was set to a solidscontent of 40% by adding NMP, and 200 μm thereof were applied and firedfor 10 min at 220° C.

The coated sheet metal was tested on the IFAM.

Example 14 Production of the Aqueous Polyurethane Dispersions Comprisinga 5% Content of (2-3% Aminopropylmethylsiloxane) DimethylsiloxaneCopolymer as a Modifier 14.1

36.15 g MDI are dissolved in 74 g butanone at 82° C. in a reactionapparatus as described in Example 13. Subsequently, 41.27 g Priplast1838, 1.43 g neopentylglycol (NPG), 6.46 g dimethanolpropionic acid(DMPA) and 7.93 g cyclohexyldimethanol (CHDM) are added in succession,and this reaction mixture is brought to reaction at 82° C. for 3 hours.After cooling to room temperature, 4.66 g of the modifier AMS-132 isadded in drops over 15 min. After a further 15 min of stirring at 50°C., 1.77 g butanol are added and the mixture is kept at 82° C. for 30min. After adding 2.14 g dimethylethylethanolamine (DMEA) over a periodof 5 min, the mixture is stirred for a further 30 min at 82° C. Aftercooling to 65° C., 9.64 g butylglycol are added and the mixture isstirred for 30 min. Subsequently, 138.6 g water are added. Subsequently,the butanone is distilled off from the resulting dispersion on therotary evaporator.

The resulting product is set to a solids content of 40% (measured at 1hour, 130° C. in the circulating furnace) by adding water.

The polyurethane dispersion is set to a solids content of 25%, a 200 μmwet film thickness is applied using a doctor blade, and it is fired at100° C. for 10 min.

Polyurethane 6 (solids = 40%) Chemicals n M [g/mol] Butanone 72.11 MDI1.05 250.25 Priplast 1838 0.15 NPG 0.1 104.16 DMPA 0.35 134.16 CHDM 0.4144.2 Modifier 5000 Butanol 0.174 74.12 DMEA 0.175 89.14 Butylglycol0.593 118.18 Bidest14.2

52.55 g MDI are dissolved in 85.9 g butanone at 82° C. in a reactionapparatus as described in Example 13. Subsequently, 40 g Priplast 1838,2.08 g neopentylglycol (NPG), 9.38 g dimethanolpropionic acid (DMPA) and12.96 g cyclohexyldimethanol (CHDM) are added in succession, and thisreaction mixture is brought to reaction at 82° C. for 3 hours. Aftercooling to room temperature, 6.13 g of the modifier AMS-132 is added indrops over 15 min. After a further 15 min of stirring at 50° C., 2.58 gbutanol are added and the mixture is kept at 82° C. for 30 min. Afteradding 3.12 g dimethylethylethanolamine (DMEA) over a period of 5 min,the mixture is stirred for a further 30 min at 82° C. After cooling to65° C., 14 g butylglycol are added and the mixture is stirred for 30min. Subsequently, 176.6 g water are added. Subsequently, the butanoneis distilled off from the resulting dispersion on the rotary evaporator.

The resulting product is set to a solids content of 40% (measured at 1hour, 130° C. in the circulating furnace) by adding water.

The polyurethane dispersion is set to a solids content of 30%, a 200 μmwet film thickness is applied using a doctor blade, and it is fired at100° C. for 10 min.

Polyurethane 9 (solids = 40%) Chemicals n M [g/mol] Butanone 72.11 MDI1.05 250.25 Priplast 1838 0.1 NPG 0.1 104.16 DMPA 0.35 134.16 CHDM 0.45144.2 Modifier 5000 Butanol 0.174 74.12 DMEA 0.175 89.14 Butylglycol0.593 118.18 Bidest14.3

52.55 g MDI are dissolved in 90 g butanone at 82° C. in a reactionapparatus as described in Example 1. Subsequently, 30 g Priplast 1838,2.08 g neopentylglycol (NPG), 9.38 g dimethanolpropionic acid (DMPA) and13.68 g cyclohexyldimethanol (CHDM) are added in succession, and thisreaction mixture is brought to reaction at 82° C. for 3 hours. Aftercooling to room temperature, 5.66 g of the modifier AMS-132 is added indrops over 15 min. After a further 15 min of stirring at 50° C., 2.58 gbutanol are added and the mixture is kept at 82° C. for 30 min. Afteradding 3.12 g dimethylethylethanolamine (DMEA) over a period of 5 min,the mixture is stirred for a further 30 min at 82° C. After cooling to65° C., 14 g butylglycol are added and the mixture is stirred for 30min. Subsequently, 164.4 g water are added. Subsequently, the butanoneis distilled off from the resulting dispersion on the rotary evaporator.

The resulting product is set to a solids content of 40% (measured at 1hour, 130° C. in the circulating furnace) by adding water.

The polyurethane dispersion is set to a solids content of 30%, a 200 μmwet film thickness is applied using a doctor blade, and it is fired at100° C. for 10 min.

Polyurethane 10 (solids = 40%) Chemicals n M [g/mol] Butanone 72.11 MDI1.05 250.25 Priplast 1838 0.075 NPG 0.1 104.16 DMPA 0.35 134.16 CHDM0.475 144.2 Modifier 5000 Butanol 0.174 74.12 DMEA 0.175 89.14Butylglycol 0.593 118.18 Bidest

Example 15 Synthesis Procedure for In Situ Synthesis of a PDMS GelParticle Dispersion

The disperse phase (NMP position 1) and a suitable emulsifying agent(position 2) are placed in advance in a 2 litre glass reactor having amaximally wall-to-wall anchor agitator and a reflux cooler.

The vinyl-functional PDMS prepolymer (position 3) is mixed with asuitable catalyst (position 4) filled into a dropping funnel.

The hydride-functionalised PDMS prepolymer (position 5) is filled into afurther dropping funnel.

The two prepolymers are added in drops over a period of approximately 10min with intensive stirring.

(By way of the catalyst selection, the necessary reaction temperaturecan be varied from room temperature to over 100° C.)

The mixture is stirred intensively for a further 5 hours andsubsequently stirred slowly for 20 hours.

Example recipe GP2002:

Raw Chem. Molar Function- Equivalent Masses Pos. material name massality [%] [%] 1 Disperse N-methyl- 79.496 phase pyrrolidone 2 Emulsi-Silicon 0.3 fying glycol agent D.C. copolymer Fluid 190 3 ABCR: Divinyl-800 2 47.3 5.6 DMS V05 terminated poly- dimethyl- siloxane (prepolymer)4 ABCR: Pt Catalyst 0.204 SIP (active at 6830.3 room temp.) 5 ABC:Methyl- 6000 6.49 52.7 14.4 HMS-082 hydro- siloxane dimethyl- siloxanecopolymer (prepolymer) TOTAL: 100.00 100.00

The dispersion obtained of crosslinked PDMS gel particles is worked intoconventional NMP-based polyamide-imide electrical insulation enamel (forexample using Dispermats or Ultra-Turraxes).

Content of the dispersion in the “blend”:

1-75 (PDMS gel particle dispersion); preferably 5-20%; particularlypreferably approx. 10%

Advantages of this synthesis and of the PDMS gel particles obtained:

The mesh width of the crosslinked gel particles can be controlled by wayof the functionality and molar mass of the prepolymers.

As a result of using monovinyl-functional prepolymers, “dangling ends”(free polymer ends) can be introduced, and gel particles having a PDMSbrush surface can be produced.

As a result of using an excess of divinyl-functional prepolymers,“dangling ends” (free polymer ends) can similarly be introduced, and gelparticles having a PDMS brush surface can be produced.

As a result of the crosslinking within the gel particles, the migrationcapacity of the siloxanes is suppressed.

As a result of the in situ synthesis in NMP, the dispersion obtained canbe worked directly into an NMP-based electrical insulation enamel.

The dispersion obtained of crosslinked PDMS gel particles can be workedinto an NMP-based electrical insulation enamel as an additive; as aresult of “missing” polyether segments, the thermal stability isincreased by comparison with conventional lubricant additives (polyetherpolydimethylsiloxane copolymers)

Example 16 Application Tests Using PDMS Gel Particle Dispersions

Table 5 shows mixtures of electrical insulation enamels and PDMS gelparticles for which application tests are carried out with subsequentfriction tests.

The PDMS gel particle dispersions were worked into a conventionalNMP-based polyamide-imide electrical insulation enamel and into amodified enamel consisting of polyamide-imide polydimethylsiloxane blockcopolymers having a 20% PDMS content.

TABLE 5 Content of modified poly- Content Content Content Content amide-of of of of non- imide Friction PDMS PDMS PDMS modified enamel test, gelgel gel poly- PAI LM Parusel particle particle particle amide- 28C30CCoF Friction disper- disper- disper- imide (20% (DIN test, sion sionsion enamel PDMS EN Scintilla GP 2001 GP 2002 GP 2007 595/30 content)60851) [N] — 10% — 90% — 0.115 5.5 — 40% — 60% — 0.180 7.75 — 75% — 25%— 0.195 8.0  40% — — 60% — 0.174 8.5 100% — — — — 0.241 7.25 — 10% — —90% 0.127 5.5 — 40% — — 60% 0.139 7.5 — 75% — — 25% 0.141 7.0 Control:pure PAI 100%  0.230 14.0

Sliding Capacity Test

As well as testing the thermal resistance and electrical properties, thesliding capacity was determined by two methods.

1. Measuring the Surface Resistance in Accordance with ParuselCoefficient of Friction

When the surface resistance is measured in accordance with the Paruselcoefficient of friction, an enamelled wire is passed between a polishedsteel surface and a steel slide lying thereon. The force which acts onthe steel slide is measured. This results in a (dimensionless)coefficient of friction. Low values of the coefficient of friction meanlow friction (tensiometry, see DIN EN 60851).

2. Measuring the Frictional Resistance in Accordance with Scintilla

An enamelled wire is passed at high speed under a steel block having aparticular contact surface area. The force which is produced by thefriction is measured. The result is in newtons (N).

1.-31. (canceled)
 32. An electrical insulation enamel comprising apolymer comprising a base polymer and modifying units which areincompatible with the base polymer after the polymer has cured, whereinthe base polymer is selected from the group consisting ofpolyamide-imides, polyester-imides, polyamides, polyurethanes,polyimides, polyester-amide-imides, polyepoxides, and mixtures orcombinations thereof, wherein the modifying units arepolydialkylsiloxanes which comprise 40 to 500 Si units.
 33. Theelectrical insulation enamel of claim 32, comprising separate regions onthe surface of the cured enamel after the polymer has cured.
 34. Theelectrical insulation enamel of claim 32, wherein the modifying unitsare polydimethylsiloxanes.
 35. The electrical insulation enamel of claim32, wherein the base polymer is a polyamide-imide and/or apolyester-imide.
 36. A cured electrical insulation enamel which can beobtained by thermally curing the electrical insulation enamel of claim32, comprising separate regions on the surface of the cured electricalinsulation enamel.
 37. A process for producing the electrical insulationenamel of claim 32, comprising: polymerizing a first modified block, forexample a monomer or a prepolymer, which comprises at least onemodifying unit, with at least one second monomer, so as to obtain apolymer comprising modifying units; and, formulating the polymercomprising modifying units with a solvent and optionally additives so asto form an electrical insulation enamel.
 38. A process for producing acoated wire, comprising: polymerizing a first modified block, forexample a monomer or a prepolymer, with at least one modifying unitcomprising at least a second monomer, so as to obtain a polymercomprising modifying units; formulating the polymer comprising modifyingunits with a solvent and optionally additives so as to form anelectrical insulation enamel; applying the electrical insulation enamelto a wire; and, subjecting the wire with the applied electricalinsulation enamel to a firing process, there being separate regions onthe surface of the cured electrical insulation enamel.
 39. A wire coatedwith the electrical insulation enamel of claim
 32. 40. A wire comprisingelectrical insulation enamel without modifying units wherein theelectrical insulation enamel of claim 32 is applied, as an outer layeror layers, to the wire.
 41. A wire, in particular a copper wire, coatedwith the electrical insulation enamel of claim
 36. 42. A wire, inparticular a copper wire, comprising an electrical insulation enamelwithout modifying units and an outer layer or layers of the electricalinsulating enamel of claim
 36. 43. A coil comprising the wire of claim41.
 44. An electrical insulation enamel, comprising a polymer andpolydialkylsiloxane gel particles, wherein the polymer is selected fromthe group consisting of polyamide-imides, polyester-imides,polyurethanes, polyesters, polyamides, polyimides,polyester-amide-imides, and mixtures or combinations thereof.
 45. Theelectrical insulation enamel of claim 44, comprising separate regions onthe surface of the cured enamel after the polymer has cured.
 46. Theelectrical insulation enamel of claim 44, comprisingpolydimethylsiloxane gel particles.
 47. The electrical insulation enamelof claim 44, wherein the polymer is a polyamide-imide.
 48. A curedelectrical insulation enamel which can be obtained by thermally curingthe electrical insulation enamel of claim
 44. 49. A process forproducing the electrical insulation enamel of claim 44, comprisingmixing a polysiloxane gel particle dispersion and an enamel whichcontains a polymer.
 50. The process of claim 49, wherein the enamelwhich contains the polymer is a conventional enamel or the electricalinsulation enamel of claim
 32. 51. A wire, in particular a copper wire,comprising the electrical insulation enamel of claim
 44. 52. A wire, inparticular a copper wire, coated with the electrical insulation enamelof claim
 48. 53. A wire, in particular a copper wire, which comprises anelectrical insulation enamel without modifying units and an outer layeror layers comprising the electrical insulation enamel of claim
 48. 54. Acoil, comprising the wire of claim 52.